Hi Saqib, I am on I9300XXUGNB6_I9300OJVGNB3_PAK
and only this method by Zaroon worked for me. ([How TO] Solve Not Registered on network Galaxy S3 I9300 issue and restore IMEI | Androidveterans)
FIXES:
The Device will connect to the network right away after applying the fix.
IMEI number will be...